Method and a system for disinfecting air in air conditioning ducts

ABSTRACT

A method and system for disinfecting air in ventilation ducts, using a non-poisonous and substantially non-volatile disinfectant. The disinfectant is vaporized by micro-vaporizer, and ionization electrodes ionize the air and the disinfectant particles. An ozone sensor is located downstream of the ionization electrodes and emits a signal to a controller, which controls the voltage at the ionization electrode, and thus the production of ozone is controlled.

BACKGROUND OF THE INVENTION

1. Field of the Invention

When, in closed spaces, air is supplied by air supply and/orconditioning ducts, it is desired that irritating or harmful germs, inparticular fungi, algae, microbes, viruses and the like, not beintroduced into the space since they can harm the health or at least thecomfort of persons present therein.

2. Description of Prior Art

A disadvantage of air filters is that they will generally be unable tocompletely remove such germs, so that the germs let through can developfurther, and, when improving the filtering efficiency, the pressure dropover such filters will increase accordingly. In the case of moist andwarm air, very favorable conditions for the growth of such germs canoccur.

A good air disinfection is especially important when a substantial partof the air introduced into the closed space is recycled, as, forinstance, in airplanes.

Eliminating germs with poisonous substances is not allowed in mostcountries, if these substances can reach the space in which persons arepresent.

SUMMARY OF THE INVENTION

It is one object of this invention to provide a method for disinfectingair in ventilation ducts, in which a non-poisonous and substantiallynon-volatile disinfectant in water, preferably a quaternary ammoiniacomplex, is vaporized into the air flow in the duct by amicro-vaporizer. The air is ionized without substantial ozoneproduction, and the ionized particles are deposited on the walls of theduct. The walls of the duct are kept at ground potential with respect tothe air-ionization electrodes.

It is another object of this invention to provide a system fordisinfecting air comprising vaporizing nozzles connected to a reservoir,and ionization electrodes for ionizing the air flow. An ozone sensor ispositioned downstream of the vaporizing nozzles and ionizationelectrodes, and can control the voltage at the ionization electrodes.

The non-poisonous disinfectant kills fungi, algae and similar organisms,and is active not only in the air flow itself, but, by precipitationthereof is also active on the walls of the duct. Thus, the germsprecipitating on the walls of the duct can be effectively suppressed.When, moreover, the air is ionized, not only microbes and viruses willbe effectively suppressed, but also the vaporized disinfectant particleswill be charged, so that the disinfectant particles will deposit evenfaster on the duct walls. When the air flowing through the duct is to bemoistened, preferably the same disinfectant is added to the water usedtherefor, in order to counteract thereby the introduction of harmfulgerms into the duct.

This invention will be described below in more detail by reference to adiagram of a system according to one embodiment of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a system according to one embodiment of thisinvention.

DESCRIPTION OF PREFERRED EMBODIMENT

In the air ventilation duct 1, are consecutively arranged a flow sensor3, an assembly 4 of particularly needle-shaped air ionisationelectrodes, an assembly 5 of disinfectant vaporizers, and an ozonesensor 6. The direction of the flow of air is indicated by the arrows 2.

These elements are connected, by electric leads 7, with a controlapparatus 8 which also comprises a high-voltage source for theelectrodes 4, the vaporizers 5 being connected, by a tube 9, with a pump10 which can pump the disinfectant dissolved in water from a reservoir11.

The flow sensor 3 can disconnect the pump 10, and, if required, also theelectrodes 4, if the air flow 2 decreases below a given threshold value.It is also possible to control the operation of the pump 10 by the flowsensor 3. The ozone sensor 6 can lower the voltage at the electrodes 4if an ozone content threshold is exceeded. This voltage should,generally, be lower than 10 kV. In this manner more than 10¹² ions/s canbe produced at a current intensity of some μA.

The air ionization, in particular when producing negative ions, willcause microbes, viruses and similar micro-organisms present in the airflow to be annihilated. A very important effect of this ionization is,furthermore, that the disinfectant particles are also being charged.Thus disinfectant particles will be driven towards the duct walls,which, as indicated at 12, are grounded, so that these particles willdeposit on the duct walls. If fungi, algae or the like also deposit onthe walls, they will be killed, or at least their growth will beinhibited, by the continued contact with the disinfectant in such adegree that no dangerous growth thereof will occur.

Since the air flow in the duct 1 will, eventually, reach the working orliving space, the disinfectant should comply with the most severerequirements imposed by public health services. Therefore it should notcontain mercury, formaldehyde, phenol or the like, and, because of firehazard, in particular in the case of ionization, the use of alcohol isnot allowed either.

The disinfectant used according to one embodiment of this invention is aquaternary ammonium compound, commercially available under the name"Dessair 2000", and being approved by the Swiss inspection service asbeing non-poisonous ("Giftklasse Frei" BAG T 73512 DC).

According to one embodiment of this invention this disinfectantcomprises a benzyl ammonium chloride selected from the group consistingof n-octyldimethyl, 1,1,3,3-tetrabutyl phenoxy ethyldimethyl and1,1,3,3-tetrabutyl-o-ethoxydimethyl benzyl ammonium chloride. Theinvention is, however, not restricted to these examples.

This disinfectant is sold in concentrated form (16% active substance),and the concentrate will, for example, be added to the water in thereservoir 11 in a ratio of 1:100, so that the disinfectant has aconcentration of 0.16%. Preferably demineralized water is used therefor.

The mist particles formed by the vaporizers 5 having, for example, amean size of about 50 μm, precipitate on the walls of the duct, inparticular because they obtain a charge by the ionization of the air,causing them to be attracted towards the duct walls, and the water thenevaporates. Some decomposition may take place, which, however, will notlead to noxious products. This disinfectant is, moreover, active againstodors, in particular disagreeable odors. At the average vapor particlesize of about 50 μm, an amount of about 0.06 to 0.08 ml/m³ of thedisinfectant is vaporized in the air at a positive pressure of about0.35 MPa.

When air moistening is required, water can be vaporized in a suitablelocation of the duct 1 and under control of the control apparatus 8,and, a humidity sensor can also be used. Preferably the samedisinfectant is added to this water so as to counteract the introductionof fungi, algae and the like.

According to one embodiment of this invention the system can comprise amicroprocessor, and can be connected remotely thus allowing remotecontrol or measurement.

I claim:
 1. In a method for disinfecting air in a ventilation duct,wherein a non-poisonous and substantially non-volatile disinfectant isvaporized into the air flowing in the duct as an aerosol by means ofmicrovaporizers, the improvement comprising the steps of: first,ionizing the air flowing in the duct and thereby producing an ionizedair flow with an amount of ozone; second, electrically chargingsuspended disinfectant particles in the ionized air flow; andmaintaining an electrical potential difference between an interiorsurface of the duct and a plurality of ionization electrodes exposed tothe air flow.
 2. In a method of claim 1 wherein the disinfectant is in aconcentration of about 0.16% -in water, and an amount of about 0.06-0.08ml/m³ of the disinfectant is vaporized in the air at a positive pressureof about 0.35 MPa at an average vapor particle size of about 50 μm. 3.In a method according to claim 2, wherein the disinfectant humidifiesthe air.
 4. In a system for disinfecting air, having an air duct (1),wherein an air flow (2) is disinfected, and an assembly of vaporizingnozzles (5) are exposed to the air flow (2) and in communication with areservoir (11) containing dissolved disinfectant, the improvementcomprising: a plurality of needle-shaped ionization electrodes (4)positioned within the air duct (1) upstream of the vaporizing nozzles(5), said ionization electrodes (4) connected to a high-voltage source,an ozone sensor (6) positioned downstream of said ionization electrodes(4) and electrically coupled to a control means (8) for controlling thehigh-voltage source, and walls of the air duct (1) maintained at a fixedelectrical potential difference and being grounded with respect to saidionization electrodes (4).
 5. In a system according to claim 4, whereina metering pump (16) is in communication with said nozzles (5) and saidreservoir (11) and a flow meter (3) is positioned in the air duct (1),the flow meter (3) is electrically connected to the control means (8),and the control means (8) is electrically connected to the metering pump(10).
 6. In a method according to claim 1, wherein the disinfectanthumidifies the air.